Critical temperature error notification

External displays are not allowed in critical
thermal condition. This CL adds notification
telling user that it is not possible to enable
mirroring in this case.

Change-Id: I28d7f1d9e683e6a99bc33b00643b3129fece93b4
Test: atest ExternalDisplayPolicyTest DisplayNotificationManagerTest
Bug: 283461472
Bug: 294014929